Hydrocarbon conversion catalyst

ABSTRACT

A hydrocarbon conversion catalyst useful for converting hydrocarbon feeds to midbarrel products is prepared by extruding a mixture of a porous, inorganic refractory oxide component and a crystalline aluminosilicate zeolite having cracking activity to form extrudates which are broken into particles normally ranging in length between 1/16 and 1/2 inch. The extruded particles are then calcined in the presence of added steam at a water vapor partial pressure greater than about 2.0 p.s.i.a., preferably greater than about 5.0 p.s.i.a. The calcination step is carried out in the presence of sufficient added steam for a sufficient amount of time at a sufficient temperature to convert the crystalline aluminosilicate zeolite in the extrudates into an ultrahydrophobic zeolite having a unit cell size between about 24.20 and about 24.45 Angstroms and a sorptive capacity for water vapor less than about 5 weight percent of the zeolite at 25° C. and a p/p° value of 0.10.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.793,567, filed in the United State Patent and Trademark Office on Oct.31, 1985 (now abandoned) which is a continuation-in-part of U.S. patentapplication Ser. No. 699,919, filed in the United States Patent andTrademark Office on Feb. 8, 1985, which is a continuation of U.S. patentapplication Ser. No. 531,924, filed in the United States Patent andTrademark Office on Sept. 13, 1983 and now U.S. Pat. No. 4,517,074,which is a divisional of U.S. patent application Ser. No. 84,761, filedin the United States Patent and Trademark Office on Oct. 15, 1979 andnow U.S. Pat. No. 4,419,271.

BACKGROUND OF THE INVENTION

This invention relates to a hydrocracking process and a catalyst for usetherein. The invention is particularly concerned with a catalystcontaining an ultrahydrophobic zeolite which, when used as ahydrocracking catalyst, selectively yields middle distillates.

Petroleum refiners often produce desirable products such as turbinefuel, diesel fuel, and other products known as middle distillates, aswell as lower boiling liquids, such as naphtha and gasoline, byhydrocracking a hydrocarbon feedstock derived from crude oil. Feedstocksmost often subjected to hydrocracking are gas oils and heavy gas oilsrecovered from crude oil by distillation. A typical gas oil comprises asubstantial proportion of hydrocarbon components boiling above about700° F., usually at least about 50 percent by weight boiling above about700° F. A typical heavy gas oil normally has a boiling point rangebetween about 600° F. and 1050° F.

Hydrocracking is generally accomplished by contacting, in an appropriatereaction vessel, the gas oil or other feedstock to be treated with asuitable hydrocracking catalyst under conditions of elevated temperatureand pressure in the presence of hydrogen so as to yield a productcontaining a distribution of hydrocarbon products desired by therefiner. Although the operating conditions within a hydrocrackingreactor have some influence on the yield of the products, thehydrocracking catalyst is the prime factor in determining such yields.At the present time middle distillates are not in high demand in theUnited States, however, marketing surveys indicate that there will be anincreased demand for middle distillates as the year 2000 approaches. Forthis reason refiners have recently been focusing on midbarrelhydrocracking catalysts which selectively produce middle distillatefractions, such as turbine fuel and diesel fuel, that boil in the 300°F. to 700° F. range.

The three main catalytic properties by which the performance of amidbarrel hydrocracking catalyst is evaluated are activity, selectivity,and stability. Activity may be determined by comparing the temperatureat which various catalysts must be utilized under otherwise constanthydrocracking conditions with the same feedstock so as to produce agiven percentage, normally about 60 percent, of products boiling below700° F. The lower the activity temperature for a given catalyst, themore active such a catalyst is in relation to a catalyst of higheractivity temperature. Selectivity of hydrocracking catalysts may bedetermined during the foregoing described activity test and is measuredas the percentage fraction of the 700° F.-product boiling in themidbarrel product range of 300° F. to 700° F. Stability is a measure ofhow well a catalyst maintains its activity over an extended time periodwhen treating a given hydrocarbon feedstock under the conditions of theactivity test. Stability is generally measured in terms of the change intemperature required per day to maintain a 60 percent or other givenconversion.

As pointed out in U.S. Pat. No. 4,401,556, the disclosure of which ishereby incorporated by reference in its entirety, hydrocrackingcatalysts containing crystalline aluminosilicate zeolites generally havehigh activity but relatively poor selectivity for middle distillateproducts. Because of this, midbarrel hydrocracking catalysts normallyemploy an amorphous inorganic oxide base containing no zeoliticcomponent. Such catalysts, although selective for middle distillates,are not nearly as active as a catalyst containing a zeolitic component.U.S Pat. No. 4,401,556 discloses a midbarrel hydrocracking catalystcontaining an ultrahydrophobic crystalline aluminosilicate zeolite whichcatalyst possesses both high activity and high selectivity for producingmiddle distillates. According to the patent, the selectivity of theultrahydrophobic zeolite is abnormally high while the activity andstability of the zeolite are not impaired when compared to other knownzeolite supports. The ultrahydrophobic zeolite is prepared from a Y typezeolite starting material having a silica-to-alumina mole ratio of fromabout 4.5 to about 6.0 and a sorptive capacity for water vapor of atleast 6 weight percent at 25° C. and a p/p° value of 0.10 by calciningthe zeolite powder in an environment comprising from 0.2 to about 10atmospheres absolute of steam at a temperature ranging from 725° C. to870° C. for a period of time sufficient to reduce the zeolite's sorptivecapacity for water vapor to less than 5 weight percent at 25° C. and ap/p° value of 0.10.

Midbarrel hydrocracking catalysts have been prepared using one of theultrahydrophobic zeolites disclosed in U.S. Pat. No. 4,401,556 bysubjecting the zeolite to an ammonium exchange and then mixing theammonium-exchanged ultrahydrophobic zeolite with an inorganic refractoryoxide component and an alumina binder material. The resultant mixture isthen extruded through a die to form extrudates which are dried at 120°C. and subsequently calcined in air at 900° C. The calcined extrudatesare then impregnated with a solution of nickel and tungsten components,dried and again calcined in air. It has been surprisingly found thatdifferent batches of hydrocracking catalysts prepared in accordance withthe above-disclosed procedure have varying selectivities for middledistillates, some of which selectives are relatively low. The commercialuse of a midbarrel hydrocracking catalyst with lower than desiredselectivity for middle distillates will result in a loss of the desiredmiddle distillate product.

Accordingly, it is one of the objects of the present invention toprovide a midbarrel hydrocracking catalyst containing anultrahydrophobic zeolite, and a method for preparing such a catalyst,which is useful in hydrocracking and has high selectivity for middledistillates, which selectivity does not substantially vary from onebatch of catalyst to another. This and other objects of the inventionwill become more apparent in view of the following description of theinvention.

SUMMARY OF THE INVENTION

In accordance with the invention, it has now been found that catalystscontaining ultrahydrophobic zeolites prepared by calcining a Y zeolitepowder in steam have varying selectivities for middle distillateproducts. It is believed that this variability in selectivity is causedby the difficulty of commercially steam calcining the small particleswhich comprise the zeolite powder. It has been further found that theobserved variance in selectivities can be substantially avoided bypostponing the steam calcination step until after the Y zeolite powderhas been incorporated into the catalyst extrudates. Accordingly, theinvention is directed to a catalyst composition prepared by a process inwhich a mixture of a porous, inorganic refractory oxide component and acrystalline aluminosilicate zeolite having cracking activity is extrudedto form extrudate particles which are subsequently calcined in thepresence of added steam at a water vapor partial pressure greater thanabout 2.0 p.s.i.a., preferably greater than about 5 p.s.i.a. In anotherembodiment of the invention, a hydrocracking catalyst composition ofrelatively uniform selectivity for middle distillates is prepared asdescribed above with the additional step of incorporating at least onehydrogenation component, preferably a component containing a metalselected from Group VIA or Group VIII of the Periodic Table of Elements,into the steam calcined extrudates. As used herein "Periodic Table ofElements" refers to the version officially approved by the InternationalUnion of Pure and Applied Chemistry (IUPAC) in its 1970 rules. Anexample of such a table may be found in the inside back cover of thebook entitled "Advanced Inorganic Chemistry," fourth edition, which isauthored by F. A. Cotton and G. Wilkinson and was published in 1980 byWiley Interscience of New York.

A preferred porous, refractory oxide component for use in the catalystof the invention is a dispersion of silica-alumina in an alumina matrix.A preferred crystalline aluminosilicate zeolite for use in the catalystis prepared by a process comprising the steps of (1) ammonium exchanginga sodium Y zeolite to a sodium content between about 0.6 and 5 weightpercent, calculated as Na₂ O, (2) calcining the ammonium-exchangedzeolite at a temperature between about 600° F. and about 1650° F. in thepresence of steam at a water vapor partial pressure of at least about0.2 p.s.i.a. to reduce the unit cell size of said ammonium-exchangedzeolite to a value in the range between about 24.40 and about 24.64Angstroms, and (3) ammonium exchanging the steam calcined zeolite toreduce the sodium content of the zeolite below about 0.6 weight percent,calculated as Na₂ O.

The catalyst extrudates are normally calcined in the presence of asufficient amount of added steam and under conditions such that the unitcell size of the zeolite is reduced at least about 0.10 Angstroms to avalue between about 24.20 and about 24.45 Angstroms, preferably betweenabout 24.20 and about 24.35 Angstroms. The residence time, temperature,and water vapor partial pressure utilized during calcination of theextrudates will typically be the same as the residence time, temperatureand water vapor partial pressure required to reduce the sorptivecapacity of the zeolite for water vapor to less than about 5 weightpercent, preferably less than about 4 weight percent, of the zeolite at25° C. and a p/p° value of 0.10 if the zeolite was calcined in steamalone without first being combined with other components to formextrudates. As used herein "p/p°" represents the water vapor partialpressure to which the zeolite is exposed divided by the water vaporpartial pressure at 25° C.

Catalysts of the invention have been found to have consistently highselectivities for producing middle distillates from heavy gas oils.Since variance in catalyst selectivity for middle distillates is avoidedby postponing the steaming step until after the zeolite powder has beencombined with the refractory oxide component and other constituents ofthe catalyst in the form of extrudates, the steaming step may beincorporated into the air calcination of the extrudates, a step normallyemployed in preparing hydrocracking catalysts, thereby reducing thenumber of steps necessary to manufacture the catalyst of the inventionand also decreasing the cost of manufacturing.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with this invention, a hydrocarbon conversion catalyst isprepared by extruding a mixture of a porous, inorganic refractory oxidecomponent and a crystalline aluminosilicate zeolite having crackingactivity into extrudates which are then broken into desired lengths andcalcined in the presence of added steam at a water vapor partialpressure greater than about 2.0 p.s.i.a. As used herein "extruding"includes all forms of pelleting including tableting, extruding, prillingand the like. A midbarrel hydrocracking catalyst may be prepared byadding one or more hydrogenation components to the mixture of inorganicrefractory oxide and zeolite that is extruded or by impregnating thesteam calcined extrudates with a solution containing one or morehydrogenation components. The steam calcination step is carried out inthe presence of sufficient added and flowing steam under conditions suchthat the unit cell size of the zeolite is normally reduced at leastabout 0.10 Angstroms to a value between about 24.20 and about 24.45Angstroms. The water vapor partial pressure, residence time andtemperature utilized during the steam calcinaticn will be such that, ifthe zeolite particles were calcined alone in steam under these sameconditions prior to being composited with the inorganic refractory oxideand formed into extrudates, the sorptive capacity of the zeolite forwater vapor would be less than 5 weight percent of said zeolite at 25°C. and a p/p° value of 0.10. Thus, the zeolite in the steamed catalystextrudates will be ultrahydrophobic. Catalysts containing zeolites thatare converted to ultrahydrophobic zeolites by steaming after the zeolitehas been composited with other components and formed into extrudateshave been found to have selectivities for producing middle distillateswhich do not substantially vary from one catalyst batch to another.

The invention is based at least in part upon the discovery that, if thezeolite component of a catalyst is steamed prior to compositing thezeolite powder with the refractory oxide component and forming theextrudates, the selectivity of the resultant catalyst for middledistillate products is quite variable, with some batches having highselectivities and other batches having low selectivities. It is believedthat this variance in selectivity is the direct result of the smallparticles that comprise the zeolite powder. Such particles typicallyrange in size between about 0.10 and about 10 microns in diameter.During commercial production it is normal practice to calcine thesesmall zeolite particles in the presence of added steam in an inclinedrotary kiln furnace. The small particles of zeolite are introduced atthe entrance of the furnace from where they pass at an inclinedownwardly usually in countercurrent or cocurrent contact with steamwhich is typically introduced into the exit or entrance of the furnace.Alternately, the steam may be introduced axially into the furnacethrough a perforated pipe located in the center of the furnace andrunning the length of the furnace. Because of the small size of thezeolite particles, it is very difficult to obtain an even distributionof the particles as they flow through the furnace in contact with thesteam. Some of the particles may travel faster through the furnace thanothers, while a large number of particles may travel preferentially downthe walls of the furnace or through the center of the furnace. As aresult only a portion of the zeolite particles are subjected to steamunder the proper conditions required to convert the particles to thedesired ultrahydrophobic zeolite. In the extreme, some of the particlesmay contact so much steam that substantially all of the structuralaluminum in the particles is removed, thereby converting the zeoliteparticles into inactive quartz. Other particles may contact too littlesteam thus resulting in particles containing too much structuralaluminum. The particles of zeolite that have been nonuniformly calcinedwith steam may not have the desired unit cell size, water sorptivecapacity or other properties required of the ultrahydrophobic zeolitethat, when combined with a refractory oxide component and hydrogenationmetal components, results in a hydrocracking catalyst having a highselectivity for middle distillates.

It has been found that the above-discussed problem can be avoided byeliminating the direct steaming of the zeolite powder and insteadcompositing the zeolite powder with the refractory oxide component inthe form of extrudates which can then be subjected to steamcalcination--instead of air calcination--under conditions, including theproper water vapor partial pressure, residence time, and temperature, toconvert the original zeolite in the extrudates into the desiredultrahydrophobic zeolite. The steam calcination step may be carried inan inclined rotary kiln furnace as before but since the catalystparticles are now in the form of extrudates, which will normally have adiameter of at least about 1/32 of an inch and are much larger than theoriginal zeolite particles, they will pass uniformly through the furnacein such a fashion that the individual particles contact approximatelythe same amount of steam at about the same temperature for approximatelythe same time. The end result is the production of a catalyst which willnot have substantially different selectivities from one batch toanother.

Suitable zeolitic starting materials for use in preparing the catalystof the invention include crystalline aluminosilicate zeolites which havecatalytic activity for cracking hydrocarbons, a sorptive capacity forwater vapor greater than 6.0 weight percent of the zeolite at 25° C. anda p/p° value of 0.10, and a unit cell size between about 24.40 and about24.65 Angstroms. Examples of such zeolites include Y zeolites, modifiedY zeolites, X zeolites, and modified X zeolites. Preferably, thestarting zeolite will have a pore size above about 7.0 Angstroms, willbe comprised of 12-membered rings of oxygen atoms, and willnonselectively sorb n-hexane, 2,2-dimethylbutane and larger molecules.The most preferred zeolites for use in preparing the catalyst arecrystalline aluminosilicate Y zeolites. U.S. Pat. No. 3,130,007, thedisclosure of which is hereby incorporated by reference in its entirety,describes Y-type zeolites having an overall silica-to-alumina mole ratiobetween about 3.0 and about 6.0, with a typical Y zeolite having anoverall silica-to-alumina mole ratio of about 5.0. It is also known thatY-type zeolites can be produced, normally by dealumination, having anoverall silica-to-alumina mole ratio above 6.0. Thus, for purposes ofthis invention, a Y zeolite is one having the characteristic crystalstructure of a Y zeolite, as indicated by the essential X-ray powderdiffraction pattern of Y zeolite, and an overall silica-to-alumina moleratio above 3.0, and includes Y-type zeolites having an overallsilica-to-alumina mole ratio above about 6.0.

Both nondealuminated and dealuminated Y zeolites may be used as astarting material for preparation of the catalyst. The term"dealuminated Y zeolite" as used herein refers to a Y zeolite which hasbeen treated to remove aluminum from the framework structure of thezeolite. A dealuminated Y zeolite may have an overall silica-to-aluminamole ratio above or below 6.0 depending on whether the aluminum removedfrom the framework structure of the zeolite is also removed from thebulk zeolite. It will be understood that in converting a Y zeolitestarting material to a dealuminated Y zeolite, the resultingdealuminated zeolite may not have exactly the same X-ray powderdiffraction pattern for Y zeolites as is disclosed in U.S. Pat. No.3,130,007. The d-spacings may be shifted somewhat due to a shrinkage inthe unit cell size which is due to a decrease in framework aluminumcontent. The essential crystal structure of Y zeolite will, however, beretained so that the essential X-ray powder diffraction pattern of thedealuminated zeolite will be consistent with that of either Y zeoliteitself or a Y zeolite of reduced unit cell size.

The stability and/or acidity of the starting zeolite, whetherdealuminated or nondealuminated, may be increased by exchanging thezeolite with ammonium ions, polyvalent metal cations, such as rareearth-containing cations, magnesium cations or calcium cations, or acombination of ammonium ions and polyvalent metal cations, therebylowering the sodium content until it is less than about 0.8 weightpercent, preferably less than about 0.5 weight percent and mostpreferably less than about 0.3 weight percent, calculated as Na₂ O.Methods of carrying out the ion exchange are well known in the art.

A preferred Y zeolite for use as the starting zeolite in preparing thecatalyst of the invention is one produced by first ammonium exchanging aY zeolite to a sodium content between about 0.6 and 5 weight percent,calculated as Na₂ O, calcining the ammonium-exchanged zeolite at atemperature between about 600° F. and 1650° F. in the presence of steamat a water vapor partial pressure of at least 0.2 p.s.i.a. to reduce theunit cell size of the ammonium-exchanged zeolite to a value in the rangebetween about 24.40 and 24.64 Angstroms, and then ammonium exchangingthe steam calcined zeolite to replace at least 25 percent of theresidual sodium ions and obtain a zeolite product of less than about 1.0weight percent sodium, preferably less than about 0.6 weight percentsodium, calculated as Na₂ O. Such a Y zeolite is highly stable andmaintains a high activity. The zeolite is described in detail in U.S.Pat. No. 3,929,672, the disclosure of which is hereby incorporated byreference in its entirety. The same or a similar zeolite is sold by theLinde Division of Union Carbide Corporation as LZY-82 zeolite. Otherpreferred Y zeolites are prepared in the same manner as described aboveexcept that instead of exchanging the steam calcined zeolite withammonium ions, the zeolite is leached with a solution of an organicchelating agent, such as EDTA, or an inorganic or organic acid.Preferably, the steam calcined zeolite is leached with a dilute solutionof hydrochloric or sulfuric acid ranging in concentration between about0.01 N and about 10 N. Zeolites prepared in the above-described mannerare disclosed in U.K. patent application No. 2,114,594 published Aug.24, 1983, the disclosure of which is hereby incorporated by reference inits entirety.

A group of Y zeolites from which the starting zeolite for preparing thecatalyst of the invention may be selected is comprised of dealuminatedzeolites normally having an overall silica-to-alumina mole ratio aboveabout 6.0, preferably between about 6.1 and about 16. The zeolites ofthis group are prepared by dealuminating a Y zeolite having an overallsilica-to-alumina mole ratio below about 6.0 and are described in detailin U.S. Pat. No. 4,503,023, the disclosure of which is herebyincorporated by reference in its entirety. A preferred member of thisgroup is known as LZ-210, a zeolitic aluminosilicate molecular sieveavailable from the Linde Division of the Union Carbide Corporation.LZ-210 zeolites and other zeolites of this group are convenientlyprepared from a Y zeolite starting material in overall silica-to-aluminamole ratios between about 6.0 and about 20, although higher ratios arepossible. Preferred LZ-210 zeolites have an overall silica-to-aluminamole ratio of about 6.1 to about 16. Typically, the unit cell size is ator below 24.65 Angstroms and will normally range between about 24.40 andabout 24.60 Angstroms. LZ-210 zeolites having an overallsilica-to-alumina mole ratio below 20 generally have a sorptive capacityfor water vapor of at least 20 weight percent based on the anhydrousweight of the zeolite at 25° C. and 4.6 millimeters mercury water vaporpartial pressure. Normally, the oxygen sorptive capacity at 100millimeters mercury and -183° C. will be at least 25 weight percent. Ingeneral, LZ-210 zeolites are prepared by treating Y zeolites with anaqueous solution of a fluorosilicate salt, preferably a solution ofammonium hexafluorosilicate.

In accordance with the invention, the Y zeolite or other crystallinealuminosilicate zeolite starting material is combined with a porous,inorganic refractory oxide component, or a precursor thereof, such asalumina, silica, titania, magnesia, zirconia, beryllia, silica-alumina,silica-magnesia, silica-titania, other such combinations and the like.Examples of precursors that may be used include peptized alumina,alumina gel, hydrated alumina, silica-alumina hydrogels and silica sols.Normally, the porous, inorganic refractory oxide component or precursorthereof is mixed or comulled with the aluminosilicate zeolite in amountssuch that the final dry catalyst mixture will comprise (1) between about2 and about 80 weight percent zeolite, preferably between about 10 andabout 70 weight percent, and (2) between about 30 and about 98 weightpercent porous, inorganic refractory oxide, preferably between about 30and about 90 weight percent.

A preferred porous, inorganic refractory oxide component for use inpreparing the catalyst is a heterogeneous dispersion of finely dividedsilica-alumina in an alumina matrix. Such a material is described indetail in U.S. Pat. Nos. 4,097,365 and 4,419,271, the disclosures ofwhich are hereby incorporated by reference in their entireties. Oneconvenient method of preparing the dispersion is to comull an aluminahydrogel with a silica-alumina cogel in hydrous or dry form.Alternately, the alumina hydrogel may be comulled with a "graftcopolymer" of silica and alumina that has been prepared for example, byfirst impregnating a silica hydrogel with an alumina salt and thenprecipitating alumina gel in the pores of the silica hydrogel by contactwith ammonium hydroxide. In the usual case, the cogel or copolymer ismulled with the alumina hydrogel such that the cogel or copolymercomprises between about 5 and 75 weight percent, preferably 20 to 65weight percent of the mixture. The overall silica content of theresulting dispersion on a dry basis is normally between about 1 andabout 75 weight percent, preferably between about 5 and about 45 weightpercent. Typically, the silica-alumina is dispersed in a gamma aluminamatrix.

The dispersion of silica-alumina in an alumina matrix or other porous,inorganic refractory oxide component is mulled, normally in the form ofa powder, with the starting zeolite powder. If desired, a binder such asCatapal alumina may also be incorporated into the mulling mixture, asalso may one or more active metal hydrogenation components such asammonium heptamolybdate, nickel nitrate, ammonium metatungstate, cobaltnitrate and the like. After mulling, the mixture is extruded through adie having openings of a cross sectional size and shape desired in thefinal catalyst particles. For example, the die may have circularopenings to produce cylindrical extrudates or openings in the shape of3-leaf clovers so as to produce an extrudate material similar to thatshown in FIGS. 8 and 8A of U.S. Pat. No. 4,028,227, the disclosure ofwhich is hereby incorporated by reference in its entirety. Amongpreferred shapes for the die openings are those that result in particleshaving surface-to-volume ratios greater than about 100 reciprocalinches. If the die opening is not circular in shape, it is normallydesirable that the opening be in a shape such that the surface-to-volumeratio of the extruded particles is greater than that of a cylinder.After extrusion, the extruded catalyst particles are broken into lengthsof from 1/16 to 1/2 inch. The effective diameter of the extrudedparticles will normally range between about 1/40 and 1/8 of an inch. Theextruded particles will be quite large when compared to the size of thezeolite particles that are mulled to form the material that is extruded.Normally, the effective diameter of the extruded particles will rangebetween about 50 and about 200 times greater than the diameter of thezeolite particles.

After the extruded catalyst particles are broken into the desiredlengths, they are subjected to steam calcination by heating theextrudate particles in the presence of water vapor to at least about500° C., usually between about 600° C. and about 870° C., and preferablyin the range between about 700° C. and about 850° C. The steamcalcination is normally carried out at a total pressure ranging betweenabout 7.5 p.s.i.a. and about 3000 p.s.i.a., preferably between about 15p.s.i.a. and above 1500 p.s.i.a. The water vapor partial pressure duringthe steam calcination will usually range from above about 2.0 p.s.i.a.to about 150 p.s.i.a., preferably from about 5.0 p.s.i.a. to about 35p.s.i.a. In a preferred embodiment, the steam calcination step isperformed in the presence of a gaseous atmosphere consisting essentiallyof water vapor and most preferably at about atmospheric pressure.

The steam calcination is generally carried out for a period of timecorrelated with the severity of the calcination conditions, especiallythe water vapor partial pressure and the calcination temperature, so asto convert the zeolite in the extrudates to an ultrahydrophobic zeolite.The desired ultrahydrophobic zeolites have a unit cell size betweenabout 24.20 and about 24.45 Angstroms, preferably between about 24.20and 24.35 Angstroms, and a sorptive capacity for water vapor less thanabout 5 weight percent, preferably less than about 4 weight percent, ofthe zeolite at 25° C. and a p/p° value of 0.10. The zeolites are thesame or similar to the UHP-Y zeolites disclosed in U.S. Pat. No.4,401,556 and U.K. patent No. 2,014,970 published on June 29, 1982, thedisclosure of the latter patent being hereby incorporated by referencein its entirety. According to these references, a UHP-Y zeolite isdefined as a zeolite having a silica-to-alumina mole ratio of from 4.5to 35, the essential X-ray powder diffraction pattern of zeolite Y, anion exchange capacity of not greater than 0.070, a unit cell size from24.20 to 24.45 Angstroms, a surface area of at least 350 meters² /gram(B-E-T), a sorptive capacity for water vapor less than 5 weight percentat 25° C. and a p/p° value of 0.10, and a Residual Butanol Test Value ofnot more than 0.4 weight percent. The Residual Butanol Test is a measureof the adsorptive selectivity of zeolite adsorbents for relativelynonpolar organic molecules under conditions in which there is activecompetition between water and less polar molecules for adsorption on thezeolite. The test procedure is described in detail in theabove-identified patents.

Preferably the steam calcination is carried out under conditions suchthat the ultrahydrophobic zeolite formed during the calcination has asilica-to-alumina mole ratio between about 4.5 and about 9, theessential X-ray powder diffraction pattern of zeolite Y, an ion-exchangecapacity of not greater than 0.070, and a Residual Butanol Test Value ofnot more than 0.4 weight percent. More preferably, the steam calcinationis carried out under conditions such that LZ-10 zeolite is formed. LZ-10zeolite is a modified Y zeolite having a silica-to-alumina mole ratiobetween about 4.5 and about 6.0, a surface area between about 500 and700 meters² /gram, a unit cell size between about 24.20 and about 24.35Angstroms, and a sorptive capacity for water vapor less than about 5percent by weight of the zeolite at 25° C. and a p/p° value of 0.10.

The steam calcination treatment may be carried out by any number ofprocedures. In one method, the wet extrudates are merely heated in anenclosed vessel which prevents the escape of water vapor generated insitu. Alternatively, the extrudates may be heated in an autoclaveequipped with a pressure relief valve such that superatmosphericpressures of steam may be obtained therein. In yet another procedure,the extrudates may be introduced into a batch or continuous static bedcalcination zone into which preheated steam or humidified air is alsointroduced. Most preferably, however, the extrudates are calcined in aninclined rotary kiln furnace by introducing the extrudates into the kilnat the entrance so that they pass downwardly at an incline in contactwith steam that is introduced into the exit of the furnace, into theentrance of the furnace, or through a perforated pipe located in thecenter of the furnace and running the length of the furnace. Because therelatively small zeolite particles are incorporated into the relativelylarge extrudate particles, which because of their size are uniformlycontacted with steam during the calcination step, the zeolite particlesare easily and consistently converted to the desired ultrahydrophobiczeolite.

As mentioned previously, hydrogenation components may be mulled with thezeolite and the porous, inorganic refractory oxide component to form theextrudates which are subsequently subjected to steam calcination.Alternatively, the hydrogenation components may be added by impregnationafter the steam calcination step. The hydrogenation component orcomponents may be impregnated into the steam calcined extrudates from aliquid solution containing the desired hydrogenation component orcomponents in dissolved form. In some cases it may be desirable to ionexchange the steam calcined extrudates with ammonium ions prior toadding the hydrogenation metal component or components. This may be doneby slurrying the extrudates in a solution of an ammonium salt until thesodium content of the extrudates is decreased below about 0.2 weightpercent, calculated as Na₂ O. Hydrogenation components suitable forincorporation into the catalyst extrudates comprise metals selected fromGroup VIII or Group VIA of the Periodic Table of Elements. Preferredhydrogenation components comprise metals selected from the groupconsisting of platinum, palladium, cobalt, nickel, tungsten andmolybdenum. In some cases, it may be desirable that the catalyst containat least one Group VIII metal component and at least one Group VIA metalcomponent. When this is the case, the preferred combination willnormally be a nickel and/or cobalt component with a molybdenum and/ortungsten component.

If the hydrogenation component comprises a noble metal, it is generallydesired that the dissolved hydrogenation component be present in theimpregnation liquid in a proportion sufficient to ensure that thecatalyst contains between about 0.05 and about 10 weight percent of thehydrogenation component, preferably between about 0.10 weight percentand about 3.0 weight percent, calculated as the metal. If thehydrogenation component comprises a non-noble metal, however, it isnormally desired that the dissolved hydrogenation component be presentin the impregnation liquid in a proportion sufficient to ensure that thecatalyst contains between about 1.0 and about 40 weight percent of thehydrogenation component, preferably between about 10 weight percent andabout 30 weight percent, calculated as the metal oxide. After thesteamed extrudates have been impregnated with the solution containingthe hydrogenation component or components, the particles are dried andcalcined in air to produce the finished catalyst particles.

Hydrocarbon conversion catalysts prepared as described above are usefulin the conversion of a wide variety of hydrocarbon feedstocks tomidbarrel products boiling in the range between about 300° F. and about700° F. If the catalyst does not contain a hydrogenation component, itmay be utilized in the absence of added hydrogen as a catalyst forconverting hydrocarbons to more valuable products by acid catalyzedreactions, such as catalytic cracking, isomerization of n-paraffins toisoparaffins, isomerization of alkyl aromatics, alkylation, andtransalkylation of alkyl aromatics. If the catalyst contains one or morehydrogenation components, it may be used to convert feedstocks in thepresence of added hydrogen to a midbarrel hydroconversion productboiling between about 300° F. and about 700° F. The feedstocks that maybe subjected to hydrocarbon conversion by the method of the inventioninclude mineral oils, and synthetic oils such as shale oil, oil derivedfrom tar sands, coal liquids and the like. Examples of appropriatefeedstocks for hydroconversion include straight run gas oils, vacuum gasoils, and catalytic cracker distillates. Preferred hydroconversionfeedstocks include gas oils and other hydrocarbon fractions having atleast 50 weight percent of their components boiling above 700° F.

The catalyst of the invention will usually be employed as a fixed bed ofcatalytic extrudates in a hydroconversion reactor into which hydrogenand the feedstock are introduced and passed in a downwardly direction.The reactor vessel is maintained at conditions so as to convert thefeedstock into the desired product, which is normally a hydrocarbonproduct containing a substantial proportion of turbine fuel and dieselfuel components boiling in the range between 300° F. and 700° F. Ingeneral, the temperature of the reaction vessel is maintained betweenabout 450° F. and about 850° F., preferably between about 600° F. and800° F. The pressure will normally range between about 750 p.s.i.g. andabout 3500 p.s.i.g., preferably between about 1000 p.s.i.g. and about3000 p.s.i.g. The liquid hourly space velocity (LHSV) is typicallybetween about 0.3 and about 5.0, preferably between about 0.5 and 3.0.The ratio of hydrogen gas to feedstock utilized will usually rangebetween about 1000 and about 10,000 standard cubic feet per barrel,preferably between about 2000 and about 8000 standard cubic feet perbarrel as measured at 60° F. and one atmosphere.

It will be apparent from the foregoing that the invention is primarilydirected to a hydrocracking catalyst prepared in such a fashion that theselectivity of the catalyst for producing midbarrel products boilingbetween 300° F. and 700° F. from feedstocks containing a substantialproportion of material boiling above 700° F. remains constant from batchto batch. Moreover, the procedure for preparing the catalyst results ina less complicated and cheaper method of catalyst manufacturing.

Although this invention has been primarily described in conjunction withpreferred embodiments thereof, it is evident that many alternatives,modifications and variations will be apparent to those skilled in theart in light of the foregoing description. Accordingly, it is intendedto embrace within the invention all such alternatives, modifications andvariations that fall within the spirit and scope of the appended claims.

I claim:
 1. A process for making a hydrocarbon conversion cataylst whichcomprises:(a) extruding a mixture of a porous, inorganic refractoryoxide component and a crystalline aluminosilicate zeolite havingcracking activity to form extrudates; and (b) calcining said extrudatesin the presence of added steam at a water vapor partial pressure greaterthan about 2.0 p.s.i.a. under conditions such that the unit cell size ofsaid crystalline aluminosilicate zeolite is reduced to a value betweenabout 24.20 and about 24.35 Angstroms.
 2. A process as defined by claim1 wherein the water vapor partial pressure of said added steam and thetemperature and time of said calcination are such that, if saidaluminosilicate zeolite was calcined in steam alone without first beingmixed and extruded with said refractory oxide component, the water vaporsorptive capacity of said aluminosilicate zeolite would be less thanabout 5 weight percent of said zeolite at 25° C. and a p/p° value of0.10.
 3. A process as defined by claim 1 which further comprisesimpregnating said calcined extrudates with at least one hydrogenationcomponent.
 4. A process as defined by claim 3 wherein said calcinedextrudates are impregnated with a Group VIII metal hydrogenationcomponent and a Group VIA metal hydrogenation component.
 5. A process asdefined by claim 1 wherein said crystalline aluminosilicate zeolite usedin step (a) comprises LZY-82 zeolite.
 6. A process as defined by claim 1wherein said mixture is extruded through a die having a shape thatresults in extrudates having a surface-to-volume ratio greater than thatof a cylinder.
 7. A process as defined by claim 1 comprising the furtherstep of ion exchanging said calcined extrudates with ammonium ions tofurther reduce the sodium content of said extrudates.
 8. A process asdefined by claim 6 wherein said die has the shape of a three-leafclover.
 9. A process as defined by claim 4 wherein said Group VIA metalhydrogenation component comprises a tungsten component or a molybdenumcomponent and said Group VIII metal hydrogenation component comprises anickel component or a cobalt component.
 10. A process as defined byclaim 1 wherein said porous, inorganic refractory oxide componentcomprises a dispersion of silica-alumina in gamma alumina.
 11. A processas defined by claim 1 wherein said crystalline aluminosilicate zeoliteused in step (a) comprises LZ-210 zeolite.
 12. A process as defined byclaim 1 wherein said crystalline aluminosilicate zeolite used in step(a) is preparad by a process comprising (1) ammonium exchanging a sodiumY zeolite to a sodium content between about 0.6 and about 5 weightpercent, calculated as Na₂ O, (2) calcining the ammonium-exchangedzeolite at a temperature between about 600° F. and about 1650° F. in thepresence of steam at a water vapor partial pressure of at least about0.2 p.s.i.a. to reduce the unit cell size of said ammonium-exchangedzeolite to a value in the range between about 24.40 and about 24.64Angstroms, and (3) leaching the steam-calcined zeolite with a solutionof hydrochloric acid having a concentration between about 0.1 N andabout 1.0 N.
 13. A process as defined by claim 1 wherein said extrudatesare formed by extruding a mixture of a porous, inorganic refractoryoxide component, a crystalline aluminosilicate zeolite having crackingactivity and at least one hydrogenation component.
 14. A process asdefined by claim 1 wherein said water vapor partial pressure is betweenabout 5 p.s.i.a. and about 35 p.s.i.a.
 15. A process as defined by claim1 wherein said mixture is extruded in the shape of cylinders.
 16. Aprocess for making a hydrocarbon conversion catalyst which consistsessentially of:(a) extruding a mixture of a porous, inorganic refractoryoxide component and a crystalline aluminosilicate zeolite havingcracking activity to form extrudates; (b) calcining said extrudates inthe presence of added steam at a water vapor partial pressure greaterthan about 2.0 p.s.i.a. under conditions such that the unit cell size ofsaid crystalline aluminosilicate zeolite is reduced to a value betweenabout 24.20 and about 24.35 Angstroms; and (c) impregnating saidcalcined extrudates with at least one hydrogenation metal component. 17.A process as defined by claim 16 wherein the water vapor partialpressure of said added steam and the temperature and time of saidcalcination are such that, if said aluminosilicate zeolite was calcinedin steam alone without first being mixed and extruded with saidrefractory oxide component, the water vapor sorptive capacity of saidaluminosilicate zeolite would be less than about 5 weight percent ofsaid zeolite at 25° C. and a p/p° value of 0.10.
 18. A process asdefined by claim 16 wherein said crystalline aluminosilicate Y zeoliteused in step (a) comprises LZ-210 zeolite.
 19. A process as defined byclaim 16 wherein said crystalline aluminosilicate zeolite used in step(a) is prepared by a process comprising the steps of (1) ammoniumexchanging a sodium Y zeolite to a sodium content between about 0.6 andabout 5 weight percent, calculated as Na₂ O, (2) calcining theammonium-exchanged zeolite at a temperature between about 600° F. andabout 1650° F. in the presence of steam at a water vapor partialpressure of at least about 0.2 p.s.i.a. to reduce the unit cell size ofsaid ammonium-exchanged zeolite to a value in the range between about24.40 and about 24.64 Angstroms, and (3) ammonium exchanging thesteam-calcined zeolite to reduce the sodium content of the zeolite belowabout 0.6 weight percent, calculated as Na₂ O.
 20. A process for makinga hydrocarbon conversion catalyst which comprises:(a) ammoniumexchanging a sodium Y zeolite to a sodium content between about 0.6 andabout 5 weight percent, calculated as Na₂ O; (b) calcining saidammonium-exchanged zeolite at a temperature between about 600° F. andabout 1650° F. in the presence of steam at a water vapor partialpressure of at least about 0.2 p.s.i.a. to reduce the unit cell size ofsaid ammonium-exchanged zeolite to a value in the range between about24.40 and about 24.64 Angstroms; (c) ammonium exchanging thesteam-calcined zeolite from step (b) to reduce the sodium content of thezeolite below about 0.6 weight percent, calculated as Na₂ O; (d)extruding a mixture of a porous, inorganic refractory oxide componentand said ammonium-exchanged, steam-calcinad zeolite from step (c) toform extrudates; (e) calcined said extrudates in the presence of addedsteam at a water vapor partial pressure greater than about 5 p.s.i.a.under conditions such that the unit cell size of the zeolite in saidextrudates is further reduced to a value between about 24.20 and about24.35 Angstroms; and (f) impregnating said calcined extrudates with atleast one hydrogenation metal component.
 21. A process as defined byclaim 20 wherein said calcined extrudates are impregnated with a GroupVIA metal hydrogenation component and a Group VIII metal hydrogenationcomponent.
 22. A process as defined by claim 21 wherein the water vaporpartial pressure of said added steam in step (e) and the temperature andtime of said calcination in step (e) are such that if the zeolite insaid extrudates from step (c) was calcined in steam alone without firstbeing mixed and extruded with said refractory oxide component, the watervapor sorptive capacity of said zeolite would be less than about 5weight percent of said zeolite at 25° C. and a p/p° value of 0.10.
 23. Aprocess as defined by claim 22 wherein said porous, inorganic refractoryoxide component comprises a dispersion of silica-alumina in gammaalumina.
 24. A catalyst composition prepared by a process comprising:(a)extruding a mixture of a porous, inorganic refractory oxide componentand a crystalline aliminosilicate zeolite having cracking activity toform extrudates; and (b) calcining said extrudates in the presence ofadded steam at a water vapor partial pressure greater than about 2.0p.s.i.a. under conditions such that the unit cell size of saidcrystalline aluminosilicate zeolite is reduced to a value between about24.20 and about 24.35 Angstroms.
 25. A catalyst composition as definedby claim 24 wherein the water vapor partial pressure of said added steamand the temperature and time of said calcination are such that, if saidaluminosilicate zeolite was calcined in steam alone without first beingmixed and extruded with said refractory oxide component, the water vaporsorptive capacity of said aluminosilicate zeolite would be less thanabout 5 weight percent of said zeolite at 25° C. and a p/p° value of0.10.
 26. A catalyst composition as defined by claim 24 wherein saidcalcined extrudates are impregnated with at least one hydrogenationcomponent.
 27. A catalyst composition as defined by claim 24 whereinsaid porous, inorganic refractory oxide component comprises a dispersionof silica-alumina in gamma alumina.
 28. A catalyst composition asdefined by claim 24 wherein said crystalline aluminosilicate Y zeoliteused in step (a) comprises LZY-82 zeolite.
 29. A catalyst composition asdefined by claim 24 wherein said crystalline aluminosilicate zeoliteused in step (a) comprises LZ-210 zeolite.
 30. A catalyst composition asdefined by claim 24 wherein said crystalline aluminosilicate zeoliteused in step (a) is prepared by a process comprising the steps of (1)ammonium exchanging a sodium Y zeolite to a sodium content between about0.6 and about 5 weight percent, calculated as Na₂ O (2) calcining theammonium-exchanged zeolite at a temperature between about 600° F. andabout 1650° F. in the presence of steam at a water vapor partialpressure of at least about 0.2 p.s.i.a. to reduce the unit cell size ofsaid ammonium-exchanged zeolite to a value in the range between about24.40 and about 24.64 Angstroms, and (3) ammonium exchanging thesteam-calcined zeolite to reduce the sodium content of the zeolite belowabout 0.6 weight percent, calcinated as Na₂ O.